Apparatus for molding plastic materials



Oct. 17, 1961 H. A. ToULMlN, JR 3,004,290

APPARATUS FOR MOLDING PLASTIC MATERIALS Filed April 30, 1956 2Slfu-ze'as-Sheexl 1 i@ ilLl 75 FIG-I En :HMI .MRL Nl) 0 Q I. i@ u. d

INVENTOR. `z` HARRY TULMIN JR. BY #aA-fm ATToR NEYs Oct. 17, 1961 H. A.ToULMlN, JR

APPARATUS FOR MOLDING PLASTIC MATERIALS 2 Sheets-Sheet 2 A Filed April30, 1956 INVENTOR. HARRY A. TOULMIN ATTORNEYS generator to a plasticmolding press,

* arent Ollce 3,004,290 Patented Oct. 17,1951

This invention relates to Ia molding press and to a method of operationthereof, and is particularly concerned with the application of ra noveltype'of thrust Plastic molding presses of the' nature which convertgranular material to a plastic mass by the-application of heat thereto,and then compact this mass into arnold cavity under pressure, are wellknown and heretofore have taken the form of mechanically orhydraulically actuated press mechanisms.

Most modern plastics are also adapted for being handled with presses ofthis nature, but a great many of these plastic materials arecharacterizedin possessing a much higher degree of uidity than waspresent with former plastic materials. Because of this higher fluidityof the plastic materials, it becomes possibleto move the material at ahigher speed into a mold cavity. v

Such plastic material upon being chilled in the mold cavity commencesquickly to set up, and it is therefore a-lso important that the plasticmaterial be rammed into the mold cavity under a high pressure to becertain of filling completely all of the space within the mold body.

According to the present invention, a novel power developing device isemployed in connection with a plastic molding press, which permitsextremely high speed operation while at the same time exerting the highpressure on the material within the mold cavity that is necessary toobtain a sound casting.

In brief, the present invention proposes the application of a jet orrocket engine tro-a plastic molding pressrto drive the mold partsclosed, and to drive the plastic molding plunger in its materialtransferring direction.

'Ihe utilization of the present invention permits of the Vconstructionof both large and small pressing units and the operation thereof at ashigh a speed as is necessary, and with the development of whateverpressures are necessary, all without the necessity of handling larger inconnectiony with the accompanying drawings, in which: I. FIGURE l is asectional View more or yless diagrammatic of a plastic molding machineconstructed vaccording to the present invention in retracted position;

FIGURE 2 is a sectional ViewV indicated by line l2 2 on FIGURE 1,showing the manner in which the motor 'isA mounted that drives the moldparts closed, and which i also drives the molding plunger;

FIGURE 3 is a diagrammatic view showing an electric -4control circuitfor the machine;A

FIGURE 4 is a sectional View, .like FIGURE 1, but g shows a double-endedmolding machine wherein one end of the machine is alwaysjactive andtheotherA end inactive;

FIGURE -5` is" a sectional viewindicated By une s s FIGURE 6 is adiagrammatic Vview showing an elecl, tric control circuit for thearrangement of FIGURE 5.

Referring to the drawings somewhat more in detail, FIGURE 1 shows amachine comprising a frame 10 which comprises a vstationarybolster-'portion 12. that supports 'on' FIGURE 4, showing the dualmotor'mounting asso- .ciated with the machine; and A engage each other.

'the stationaryv portion 14 of a mold'that has a movable portion 16 thatmay advantageously be mounted on the end of a movable cylinder 18.Cylinder 18 is reciprocably guided inthe portions 20 and 22 upstandingfrom the bottom part foffframe 10. Y

Cylinder 18 has a bore 24`therein that communicates through ya spruepassage 26 with the cavity 28 of the mold; IA plunger 30 is reciprocablymounted in bore 24 so as to displace plastic material therefrom throughthe said its left and via a passage 42 with bore 24, and communicatesatav point rightwardly therefrom as at 44 with a hopper 46 containinggranulated plastic material lIt will be seen that when feed plunger 38moves .leftwardly the plastic'material to the left thereof is pushed'over to the point where it will drop through passage 42 on top ofplunger 30, and Ithen -upon rightward movement of plungers 30 and 38this material Iwill then drop into bore 24 ahead of plunger 30 while anew change of 'material drops from hopper 46 into bore 40 ahead ofplunger 38. As is known, this arrangement is self-regulating so that apreliminary adjustment of the plungers 30 and3r8 relative to each otheris all that is required to maintain the machine in continuous operation.

The plastic material delivered to bore 24 is `softened Vtherein or evenmadeV completely fluid by heating at least theleft end of cylinder 18 asby hot fluid delivered thereto Via con-duit means 50 and owing aboutpassage means associated with the cylinder.

Similarly, the mold parts 14 and 16 are maintained cool, so that theplastic material delivered thereto sets vup quickly by a cooling. fluidpassed through the mold parts by way of a conduitmeans 52.

The plungersV 30 and 38 .are urged rightwardly in their respective boresby a compression spring 54 bearing between the right'end of cylinder 18and a plate member 56 secured to rod 32. This plate member is alsoconnected by rod 58 with piston 60 in cylinder 62. The righ-t end ofcylinder 62 is vented and the left end thereof is connected with anaccumulator 64, so that fluid will flow from the cylinderV 62 to theaccumulator via check valve 66 and pressure relief valve 68, and will owfrom the yaccumulator to cylinder. 62 via throttle or pressure reliefvalve 70 and check valve 72.

Cross head 34 is availed of for supporting a jet or rocketpropulsionunit 74 lwhich may be supplied with fluid in any desiredmanner, but is preferably connected `with a source'76 of liquid fuelwhich is arranged to be Ysupplied thereto by exible conduit 78 thatincludes head 34'at the end of a retraction stroke, and the manualselector switch S is also closed. Energization of the relay willestablish a holding circuit therefor through a timer T, which willautomatically open the holding circuit after a predetermined time delay,energization of the relay also energizing a fuel supply valve andigniter V which will cause firing of the/,propulsion unit 74.

When the unit 74 fires; cylinder 18, plungers 30 and 38 move leftwardlyas a unit until mold parts 14 and 16 Thereafter, only plungers 30 and 38move leftwardly, and this displaces plastic material .3 from bore 24into the ymold cavity. When timer T timesr out,` the firing of 74 isinterrupted thus permitting spring 54 to commence retraction of plungers30 and 38 in their Irespective bores, while Asimultaneously` accumulator64 dischanges. through valves V70 and L72. to the left end of cylinder62V and forces plate 56 nightwardly,thus carrying with it plungers 30and 38 and cylinder 18.

vThe mold parts 14 and 16 may. vadvantageous1y-com prise automaticknockout devices,..sothat at Vthe end of a retraction stroke themoldedparts will be removed from the mold cavity. At this time, ifvswitch S is closeda new cycle will1 be initiated, but if this switchisopen` the is manually actuated. A

'It will be seen fromthe foregoingthatfthe main jet or rocket propulsionunit supplies allfof theppowerg-for Vnew cycle will beinitiatedonly.whenlthesaidswitch4 'operatingthe press,therebyeliminating pumps. and valves and heavy and-expensivel hydrauliccylinders, randnthe necessity ofmovingv largefquantities .ohydraulici-uid into and out of hydraulic Hclamping motorssandlthelike.

The modifications of 'FIGURESAQ 5 and 6 is substantially identical withthe previouslydescribed modifications, except that a double-endedmachine `isillustrated wherein one end is performing a molding operationwhile the other endis retracting.

' `The parts of the-structure FIGURE 4-which are videntical with thoseof the FIGURE l modiiicationare correspondingly numbered with theaddition of Aa subscript a tothe left Vsideof FIGURE 4 anda subscriptb.. tothe right'side of FIGURE 4. n K

' Theressential'diiference betweenA the FIGUREA modiiication' and thatof FIGURE' 1 residesinthe.- provision of two ccrmbustion-,operatd.-propulsion units 74a and 74h which iire .alternately Vso that the partsofthe device vis employed to initiate and halt operation of the. press.

Wheny relay`R'-1 is energized, a holdingcir'cuittherefor isfestablished'through a timer mechanism "T-l, which predetermines a deiinitefinterlvalof energization for" the said relay.

When' relayR-l is energized, and-thev timer is in the 50 positionfshown,the fuelsupply means and, ignitermeans `V1 for the .rocket motor74a`that`dn'ves theparts of the molding press leftw'ardly` is effective,whereas whenthe said relay is energized andthe`timer`TL-1'is in itsother position igniter means V-Z for the other rocket motor -74b 55 thatAdrives the press parts 'rightwa'r'dlybecomeseffective for apredetermined interval of time thatis `determined by 'the setting-oftimer T-l.

l From Vthe foregoing, it will -beapparent that a plastic molding pressaccording' to my'inventionV embodies thel `fewestl number of parts,particularly with respecttothe power unit, while still providing ample`power for operatingeven'the largest press, while making available atype lof powerthagt will permit exceedingly rapidV operation of 'thepress and also the high compacting forces necessary Vto, producesuperior molded work pieces by completely "the" formV of measuredcharges of solidfuel. arranged to 'burn at acontrolled Vratev in .orderto produceihegeneral 54 propulsion etect which is availed of accordingto the present invention for driving the molding press.

It will be understood that this invention is susceptible to modificationin order to adapt it to different usages and 5 conditions, and,accordingly, itis desired to comprehend such modiiications within thisinvention asmay fall within the scope of the appended'clams.

l I claim: 5 1. VIn a molding press: a press frame, a stationary moldhalf mountedin saidfframe, an injection cylinder slidable in said frame,a movable mold half mounted on the discharge end of said cylinderadapted for engaging such .stationary mold half and deiiningv a moldcavity, a plunger `rcciprocable in said cylinder to displace moldingmaterial therefrom into fsa'id,V moldca'vitygnieans .for heating thecylinder to v'soften the material therein, al hopper mounted `onrtliecylinder and feed means .operable in response to reciprocation ofthe'said'plunger inthe cylinder for feed- 7Ving molding material from'said hopper to said cylinder, spring means acting between said plungerand cylinder to resist advancing movement ofthe plunger in the cylinder,`iiuid operable means for urging said4 plunger in its revtractingdirection, combustion-operated'thrust generating means connected withsaidrplunger energizable for driving the plunger in its advancingdirection and lalso for charg- 'ing said fluid operable means, sa'idiiuid operable means andsaid .spring means. being Aoperable forreturning said plunger and said cylinderrto retractedposition upon de-`energization of said thrust generating means.

2. In a molding press: two molds, each comprising vmold halves, eachouter mold half being stationary; said outer mold halvesA beingin.spacedfacing relation, an injection'cylinder supportingeach innermold half in opposition to its pertainingo'utenmoldl half, saidinjection cylindersl being 's upportedtor sliding movement; an injectionplunger in'each 'injection cylinder, `said plungers being connectedtogether, spring means urging said plungers 'in'theirretractingjdire'ction inftheir respective `cylinlders; a pairl ofoppositely'rdirected combustion-operated 40 'thrustgenerating meansconnected with `said plungers and sequentially operable for closingdirstone mold and actu- -ating itslrelation'injection plunger, andfor thenclosing theOtherm'old 'andoperating its rela-ted injection plunger whilesimultaneously, openingfthe iirstv mentioned mold and retractingtheinjecti'on plunger related therewith.

3.*In a`molding press, a=stationary mold part, a com- -v`rplementarymovablemoid; part' adapted'v to be closed -againstthestationary mbldparttodeiine amold cavity, a k'cylinder mounted on said movable mold partand comvrnunicating with'said'mold cavity,an injection plungeryreciprocable' in said cylinderI ,for moving-molding materialtherefrom`into said"moldcavity,"spring means urging saidplunger towardjretractedpositionin said cylinder, and ajet' propelled 'means -connected withsaid plunger `-for closingsaid mold parts and` advancing said plunger`nfsaid cylinder to 'move moldingmaterial into said mold cavity, andjetpropelled meansfor causing'retraction of said plunger andopening ofsaid` mold parts.

n 4. In afmol'dingpress; a stationaryimold half, acomplementaryfmovablemold half^^deiining a`mold"cavity,

a cylindersupporting said movable moldhalf; said'cylinder communicatingwith said mold `cavity defined bytsaid mold halves, a plunger=reciprocable in` said cylinder to move molding material therefrom intosaid mold cavity, springmeans' urging s aid'y plunger towardretractedposir`t1on in said cylindennuidfoperable means urging saidplunger-toward a predetermined retracted' position, and jet propulsionmeans connected with said plunger for driving said plunger to 'injectmolding material from 'said "fcylindert'intotthe'mold cavity, saidspringbeing` operable to close said mold halves and together withsaid iiuid*operable-means bring about retraction ofrsaid plunger .andjop'ening ofsaid mold halves uponvde--energization of .said jet propulsion means. Yf' 5. In extrusiommoldingfpresspa Stationary moldhalf,

a complementary movable mold half defining a mold cavity, cylinder meanslixed to said movable mold half and movable therewith, said cylindercommunicating with said mold cavity defined by said mold halves, aplunger reciprocable in said cylinder to move molding material therefrominto said mold cavity, spring means urging said plunger toward retractedposition in said cylinder, fluid operable means coacting with saidspring means for urging said plunger toward a predetermined retractedposition, and a rocket jet propulsion means mounted on a slidablecrosshead and connected with said plunger for driving said plunger andto inject molding material from said cylinder into the mold cavity, saidspring urging movement of said movable mold half and associated jcylinder means to close said mold halves and together with said fluidoperable means bring about retraction of said plunger and opening ofsaid mold halves upon de- 5 energization of said jet propulsion means.

References Cited in the tile of this patent UNITED STATES PATENTS

